Click on Topology tool - upper tool in Surveyor.
Click on Advanced.
Go to the edge where you want to add "more land".
Click add baseboard.
More land will appear.
The topology tools also allow you to sculpt the landscape, increase the height of hills, create valleys, add water, etc.
Under advanced you and also add in a displacement map to create mountains in one shot. It's a bit complicated to explain here.
Some of the basics are found here:
/N3V Games/Trainz A New Era/resources/extras, or go to wherever you installed T:ANE, whether it's a MAC or PC.
In that folder is TANE Manual.pdf